Control of the exhaust emissions from an automotive vehicle is an essential part of automotive design and vehicle development. An automotive vehicle, for example, utilizes a catalytic converter device installed in the vehicle exhaust line to reduce the toxicity of emissions from the internal combustion engine. Vehicle exhaust emissions of concern include hydrocarbons (HC), carbon monoxide (CO), and oxides of nitrogen (NOx). It is desired to reduce these emissions to avoid health and environmental problems.
There are several types of catalytic converters known in the art. These include, for example, two-way catalytic converters and three-way catalytic converters. Each type of catalytic converter utilizes at least one catalyst. In two-way catalytic converters, which include, for example, pellet, monolith, and honeycomb types, a catalyst is used to rapidly increase exhaust temperature, oxidize carbon monoxide (CO) into carbon dioxide (CO2), and oxidize unburnt hydrocarbons (HC) into water (H2O) and carbon dioxide (CO2). In three-way converters, for example, multiple catalysts are utilized such that there is an oxidizing catalyst and a reducing catalyst. A three-way catalytic convener reduces oxides of nitrogen (NOx) to nitrogen (N2) and oxygen (O2), oxidizes carbon monoxide (CO) into carbon dioxide (CO2), and oxidizes unburnt hydrocarbons (HC) into water (H2O) and carbon dioxide (CO2).
Known in the art are various catalysts that are used in catalytic converters. Often the catalyst is a precious metal. For example, widely used catalysts include platinum (Pt), palladium (Pd), and rhodium (Rh). Also known in the art are several metrics used for measuring individual catalyst criteria and behavior. For example, light-off performance, air-to-fuel ratio performance, and steady state emissions performance are metrics by which a catalyst is evaluated. What is needed in the art, however, is a method by which multiple metrics are utilized in a manner that provides a single value representative of the overall performance of the catalyst. Additionally, what is needed in the art is a method utilizing weighting factors by which adjustments are made to the metrics for specific vehicle applications. Furthermore, what is needed in the art is a method by which different catalyst technologies are evaluated in a manner that allows for the selection of a catalyst in the advanced phase of vehicle development.